Laryngoscopes are medical devices in common use in oral and tracheal medical procedures, which may be used to obtain a view of the glottis or larynx, or to manipulate the tongue, glottis or larynx in order to facilitate insertion of endotracheal tubes or other instruments such as endoscopes, which may be separate pieces of equipment, or may be integral to a laryngoscope.
Laryngoscopes comprise insertion sections, which are the elongate part of a laryngoscope which extends into a subject's oral cavity during intubation. Insertion sections may be removably attachable to a laryngoscope body or integral parts of laryngoscopes or themselves function as laryngoscopes. As well as an insertion section, laryngoscopes typically comprises a handle which is usually elongate and which may be arranged at an angle to the proximal end of the insertion section or generally parallel to the proximal end of the insertion section, or at any angle therebetween. The insertion section and handle may be integrally formed.
Video laryngoscopes include an imaging device within the insertion section. The imaging device is typically a camera but may be a light transmission device (e.g. one or more fibre optic cables) extending to a camera which is not in the insertion section, for example, within a handle which remains outside of a subject's oral cavity in use. The imaging device may be part of the insertion section but it is also known for the imaging device to be part of the body of the laryngoscope, for example mounted to an insertion section retaining element which retains a demountable insertion section. An example of such as a device is shown in EP 1638451 (McGrath). Such devices are advantageous in that the demountable insertion section can be disposable and can protect the imaging device from contamination by bodily fluids, enabling the imaging device to be reused. The insertion section retaining element can also be a strengthening element, providing mechanical strength to the insertion section. Video laryngoscopes may have an integral screen or transmit images to a remote display through a wired or wireless interface.
Prior to the development of video laryngoscopes, intubation was typically carried out using direct laryngoscopy. In direct laryngoscopy, the intubater seeks to obtain a direct line of sight view of a subject's larynx. Some known insertion sections for laryngoscopes are substantially straight, such as Miller or Wisconsin blades. However, the blade of an insertion section is more commonly curved to better enter through a subject's oropharynx towards their larynx. For example, the most common curvature of an insertion section is what is commonly called the Macintosh curve. The curvature is relatively gentle and when inserted into a subject's oral cavity, the gently curved blade is used to lift and manipulate the tissue of the oral cavity, such as the tongue, out of the line of sight to allow an intubater a direct view of the subject's larynx.
However, video laryngoscopes enable a view of a subject's larynx to be obtained from an imaging device within the insertion section and therefore within a subject's oral cavity in use, without having to significantly lift or manipulate the tongue. This enables an indirect view of the larynx to be obtained. Some video laryngoscope insertion sections have sufficiently shallow curvature to enable a direct view to be obtained. In such cases, the ability to obtain a view of the larynx prior to intubation is of assistance but is not essential.
However, where there are anomalies within the oral cavity of the subject, or where an effective view of the larynx cannot be achieved with a direct view blade such as in instances where the subject's head and neck are not able to be moved to attain a direct line of sight of the larynx, it is often necessary to use an insertion section with a greater curvature to allow the blade to be inserted into the oral cavity. In this case, the intubater visualises the larynx indirectly using the video laryngoscope camera and screen. Insertion sections for use where a user cannot normally obtain a direct line of sight view of the larynx are referred to herein as indirect view insertion sections.
Some aspects of the invention address the technical problem of providing an insertion section of suitable shape to facilitate intubation by video laryngoscopy, particularly in relation to intubation of difficult airways. It is not uncommon for users, especially inexperienced users of video laryngoscopes, to concentrate on obtaining the best possible view from the camera of a video laryngoscope before starting to insert an endotracheal tube. In doing so, they typically insert the tip of the insertion section too far into the subject's oral cavity, elevating the epiglottis directly. This can often result in a lack of sufficient room to pass the endotracheal tube into the trachea as the tip of the insertion section is too anterior in the subject's mouth in contrast to when the tip of the insertion section is placed correctly fully into the vallecular to raise the epiglottis. This can cause a user to apply unnecessary force to try to make more room to pass the tube, or to position the tube more anteriorly. Incorrect positioning of the blade in the valecular can result in what is known as a “floppy epiglottis” (a misnomer used by users when epiglottis is lying in the line of sight of the vocal cords), usually caused by an insertion section not elevating the epiglottis appropriately to raise it out of the line of sight.
It is known to provide a substantially J-shaped insertion section, with a straight proximal region, a straight distal region and a defined bend or elbow therebetween. Likewise it is known to provide insertion sections with blades with a mixture of curved and straight sections with acute changes in angle or curvature between those sections (such as McGrath Series 5, Glidescope and Belscope) Such insertion sections may provide a reasonable view of the larynx but are difficult to insert. Some aspects of the invention seek to improve the shape of an insertion section to facilitate insertion into a subject, while enabling a good view of the larynx to be obtained. It is preferable to minimise distortion of tissue, avoid the use of excessive force and to avoid excessive friction with the subject anatomy.
Some aspects address the shape of the inferior surface of the insertion section as this surface contacts the patient's tongue during insertion. Some aspects address the shape of the insertion section as a whole, to facilitate intubation.
Some aspects of the invention seek to address the problem of users inserting an insertion section too far into a subject's mouth, or insufficiently far. It has been proposed to provide a single marking on the superior surface of a laryngoscope insertion section, indicative of a dividing line between typical depth of insertion for an adult and typical depth of insertion for a child. However, this is not satisfactory as there is a significant variation in the correct depth of insertion of an insertion section between subjects within each group, and so a single indicator line is not of practical assistance.
Some embodiments of the invention address technical problems arising from friction between an insertion section and a subject's tissues. Friction between an insertion section and tissues can cause trauma and affect the safety of an intubation. For example, the subject's lips may stick to the insertion section and become dragged over the lower incisors causing trauma and bleeding.
When intubating a subject using an indirect view laryngoscope, such as a video laryngoscope, users who were trained with traditional direct view Macintosh laryngoscopes may insert an endotracheal tube along the wrong path. During traditional direct view laryngoscopy, an endotracheal tube is run across the superior surface of the oral cavity. However, it is more appropriate to run an endotracheal tube close to the insertion section itself during indirect laryngoscopy. In insertion sections that have a steeper curve, it is most appropriate that the endotracheal tube runs close to the apex of the curve of the intermediate region of the insertion section that traverses the oral cavity. Some aspects of the invention address the problem of users inserting an endotracheal tube along a path which was appropriate for traditional Macintosh laryngoscopes, but which is not appropriate with a video laryngoscope, and more particularly an insertion section with a steep curve.